We use Quickbooks Pro things would be a struggle at best without it. Also when tax time comes we just take the back-up disk to accountant to run the buisness return off of really makes it simple for them if everything is set up right there are usually no questions about this or that and is all there for them and pretty straight forward.

We use Quickbooks Pro 2002. I couldn't run without it. But be Careful, you must use all features of it or your balances will be way off. for example if you use it to bill and receive payments but not for banking than you will show all kinds of money in a Quickbooks default account called undeposited funds. so if you try to run a balance sheet it will show that you have x amount of money in some un-known account which a bank or the IRS is going to ask you to prove where this money went and it's a hassle. Also if you are in a state where you collect sales tax on the services you perform, you must use the pay sales tax function and not just write a check out from the check reg. I had an Office manager do that for over a year and i am still paying for that mistake with St. Revenue Dept. Bottom line is use every feature and it runs your business smooth. That has been my experience with it.

I too use Quickbooks, but only because I know it from 6 years using it at our franchise.
It is pretty intimidating to a newbie with no accounting experience at all.
Quicken now offers a business version with customizable invoicing and pretty much everything a simple biz needs. Much easier for a newbie to use, and cheaper too. FWIW